Monday, January 05, 2009

Novel Space Elevator Idea Demonstrated with a Broomstick

First mooted by Russian scientist Konstantin Tsiolkovsky in 1895, the space elevator idea has captured imaginations as what would be the greatest space mission ever conceived.

The idea rests on making use of the outward centrifugal force supplied by the Earth's rotation. Imagine fixing a short length of string to a football and spinning it - the string flies outward and remains taut.

If the centrifugal force provided by the Earth is balanced with its gravitational force - making use of a space elevator cable or tether whose centre of mass is at geostationary orbit - the tether would be held taut permanently, providing a means to propel people and cargo into space.

A long-standing critical issue is how to power the "climber" that would ascend the cable into space. Prevailing ideas include delivering microwave or laser power to the climber beamed from the Earth's surface, or even from orbiting solar power collectors.

In December the private firm Eurospaceward hosted the Second International Conference on Space Elevator and Tether Design in Luxembourg to discuss such schemes.

But European Space Agency ground station engineer Mr Riise provided a markedly more simple idea.

He proposed sending power mechanically - effectively by providing a carefully timed jerk of the cable at its base.

To demonstrate, he employed a broomstick to represent the cable held in tension, and an electric sander to provide a rhythmic vibration to the bottom of the stick.

Around the broomstick's circumference he tied three brushes representing the climber with their bristles pointing downwards - meaning it took slightly more force to lower the brush assembly than to raise it.

The vibration from the sander allowed the assembly to slide upward along the broomstick as it moved slightly downward, but grip it as it moved slightly upward. The net effect: the assembly rose against gravity straight to the top of the stick.